A user equipment, UE 600, in a wireless communication system, as depicted in FIG. 1, can receive signals from a plurality of base stations, e.g. signals from a base station, BS, 101 and signals from a base station 110. The signals from BS 101 and the signals from BS 110 are transmitted using different frequency ranges, as for example in 3rd Generation Partnership Project, 3GPP, Long Term Evolution, LTE, Advanced with carrier aggregation, CA, or with dual connectivity.
The BSs may not be co-located, particularly when operating in non-contiguous, NC, CA mode, and due to transmission loss, the UE 600 experiences a received signal power for signals from BS 101, that may be different than for signals from BS 110. For example in CA, the UE observes different power levels for component carriers from BS 101 and for component carriers from BS 110. The UE 600 is capable of performing automatic gain control to improve the processing of the received signals.
However, many issues arise when attempting to perform automatic gain control for processing signals received at different frequency ranges, especially when signals received from different frequency ranges or BSs are processed using a partially common path, e.g. comprising one or more common hardware resources for the sake of reducing receiver hardware complexity and reducing power consumption.
WO2013072864 discloses a receiver comprising two branches with corresponding quadrature mixers and bandpass filters for reception of non-contiguous carrier aggregation signals. WO2013072864 discloses that two branches may be configured to having independent gain. The LNA gain may be increased to improve sensitivity if both branches are used. US20140126401 discloses an amplifier which is used to apply a common gain to aggregated carriers in a single frequency band. A common gain is determined as a function of indications of received signal quality associated with groups of aggregated carriers containing one or more of the aggregated carriers. Applying a common gain to aggregated carriers in a single frequency band may be sufficient to avoid clipping of the received signals. However, this approach may not be sufficient to reach e.g. a signal to noise ratio, SNR, necessary for errorless demodulations of signals received on both frequency ranges. Thus, US2014126401 is most likely resulting in a suboptimal processing of received signals on one of frequency ranges.
There is a need for improved solutions for gain control in a wireless receiver taking into consideration factors such as target signal quality on different frequency ranges, the desire to avoid clipping of the received signals and the need to reduce power consumption.